Key Takeaways & Executive Findings
- •• A TiO2/Co3O4-modified configuration strategy significantly enhances the structural and electrochemical stability of O3-type NaNi0.4Fe0.2Mn0.4O2 cathodes. • The resulting NFMCT cathode mitigates Jahn-Teller distortions and Na+/vacancy ordering, improving phase integrity and Na+ diffusion pathways. • NFMCT delivers a high reversible capacity of 93.7 mAh·g−1 after 550 cycles at 1 C, with superior rate performance at 2 C and 5 C. • This work provides a practical and cost-effective strategy for designing high-performance sodium-ion battery cathodes.
Abstract
Sodium-ion batteries (SIBs) have recently gained wildly interest due to the abundance of sodium, lower production costs, and better low-temperature performance compared to lithium-ion batteries (LIBs). Among various cathode materials of SIBs, O3-type NaNi0.4Fe0.2Mn0.4O2 (NFM424) demonstrates high capacity and ease of synthesis, yet suffers from structural degradation and sluggish Na+ kinetics caused by large ionic radius and strong electrostatic interactions. To overcome these issues, a configuration strategy combined with TiO2 and Co3O4 by a simple solid-state reaction method was introduced to improve structural and electrochemical stability. XRD, SEM, TEM, and various electrochemical characterizations as well as TGA/DSC tests were conducted. The resulting NaNi0.4Fe0.2Mn0.3Co0.05Ti0.05O2 (NFMCT) cathode mitigated Jahn-Teller distortions and Na+/vacancy ordering while enhancing phase integrity and diffusion pathways. The obtained NFMCT maintained 93.7 mAh·g−1 after 550 cycles at 1 C, with superior rate capabilities at 2 C and 5 C. These findings deepen the understanding of configuration strategy by using multi-element oxide and highlight a practical strategy for designing high-performance SIB cathodes.
1. Introduction
With the continuous growth in global electricity demand, the pressure on power grids has intensified significantly [1–3]. To relieve this burden and ensure the stability of power systems, efficient and scalable energy storage technologies are urgently needed, especially in the context of increasing renewable energy integration [4–6]. Although lithium-ion batteries (LIBs) have been widely adopted in current energy storage systems [7–11], concerns regarding the limited availability of lithium resources [12–13], rising material costs [14–15] and environmental impacts have restricted their large-scale deployment [16–18].
Sodium-ion batteries (SIBs) have recently emerged as a promising alternative due to the abundance of sodium, lower production costs, and environmental benefits [19–21]. Among various cathode materials, layered transition metal oxides with the general formula NaxTMO2 (2/3 < x < 1, TM = transition metal) have attracted significant attention because of their high energy density, simple synthesis processes, and diverse redox activity [22]. Different phases can be divided from the layered NaxTMO2 based on the sites’ sodium coordination [23]. By controlling sodium content and transition metal properties, phase differentiation is possible [24]. The O3 phase layered oxide has good initial Coulombic efficiency (ICE) and high capacity, making it a promising cathode material. However, structural stability deterioration by large Na+ insertion/extraction limits the applications of these materials, causing irreversible volume, structural deformations, and poor rate performance [25].
Configuration strategy has been widely employed to address these issues to improve the layered cathodes’ structural integrity and electrochemical performance. For example, our previous work successfully employed this strategy combined with Co3O4 to enhance the interface stability of O3-type layered NaNi0.4Fe0.2Mn0.4O2 (NFM424) [26]. What’s more, Titanium (Ti4+) doping has been shown to suppress phase transitions, reduce polarization, and facilitate Na+ diffusion due to its stable valence state and strong Ti–O bond [27]. However, the limited electronic conductivity of Ti4+ and the minimal contribution of Co3O4 to structural stability restrict their individual effects [28]. Although other dopants such as Mg2+, Al3+, or Zn2+ have been investigated, they often lack electrochemical activity or cause structural instability under high-voltage operations [29]. Most existing studies involving Ti and Co co-doping focus on high-Co or high-entropy compositions, which differ significantly in structure and cost from Ni–Fe–Mn-based cathodes [30]. In addition, many of these works do not use TiO2 and Co3O4 as oxide precursors or provide a systematic analysis of structural evolution or Na+ transport behavior. As a result, there is still limited understanding of how TiO2- and Co3O4-modified configuration strategy influences the electrochemical and structural performance of cost-effective O3-type NFM424 materials.
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Zidong Yu, Xiaojuan Liu, Zhicheng Liu, Ye Liu, Chao Su, Zhi Sun, Jilei Du, Tao Wei (2025). Understanding of TiO2/Co3O4-modified configuration strategy for stabilizing O3-type NaNi0.4Fe0.2Mn0.4O2 cathodes with enhanced long-term and rate performance. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3260-1
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Frequently Asked Questions
What is the main challenge addressed in this study?
The study addresses the structural degradation and sluggish Na+ kinetics of O3-type NaNi0.4Fe0.2Mn0.4O2 cathodes in sodium-ion batteries, which limit their long-term cycling and rate performance.
How does the TiO2/Co3O4-modified configuration strategy improve the cathode material?
The strategy mitigates Jahn-Teller distortions and Na+/vacancy ordering, enhances phase integrity, and improves Na+ diffusion pathways, leading to better structural and electrochemical stability.
What are the key performance metrics of the modified cathode (NFMCT)?
The NFMCT cathode maintained 93.7 mAh·g−1 after 550 cycles at 1 C, with superior rate capabilities at 2 C and 5 C.
What methods were used to characterize the materials?
XRD, SEM, TEM, TGA/DSC, and various electrochemical characterizations were conducted to analyze the structural and electrochemical properties.
What is the significance of this study for sodium-ion battery development?
The study provides a practical and cost-effective strategy for designing high-performance SIB cathodes, contributing to the advancement of sustainable energy storage technologies.
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